(1) We are applying a microprocessor-assisted scoring device to monitor sexual behavior of aging male rats, and attempting to correlate this decline with changes in the hormonal correlates associated with sexual behavior (testosterone, LH and prolactin). We will attempt to reverse or delay the behavioral decline with various hormonal treatments. (2) We are studying the hormonal response of aging male rats to stress (ether, nembutal, laparotomy, hemicastration, handling) and the effect of testicular denervation on this response. (3) We are using a recently developed nuclear exchange assay of androgen receptors in seminiferous tubules and ventral prostate gland to measure and characterize the androgen receptor to changes in reproductive activity.